&bgr;-isophorone is formed by isomerizing &agr;-isophorone in the presence of an isomerizing catalyst (an aliphatic C5-20 polycarboxylic acid) in an isomerizing-reaction unit 1. The &bgr;-isophorone thus formed is oxidized with oxygen in an inert solvent in the presence of an oxidizing catalyst (a complex salt of a transition metal and an N,N′-disalicylidenediamine) in an oxidizing-reaction unit 2, thereby forming ketoisophorone. After removing a low-boiling point component, which is an impurity (non-conjugated cyclic ketone), from the reaction mixture using a distilling unit 3, a high-boiling component (oxidizing catalyst) is separated in a distilling unit 4, and then ketoisophorone is separated from the solvent in the separation unit 5. Thereafter, the solvent containing 0 to 5,000 ppm (weight basis) of the impurities and substantially free from ketoisophorone is recycled to the oxidizing reaction through a recycling line 6. According to the present invention, the combination of the isomerizing reaction and the oxidizing reaction makes it possible to produce ketoisophorone from &agr;-isophorone while maintaining the activity of the oxydizing catalyst.
-异樟酮是通过在异构化反应装置1中,在异构化催化剂(一种脂肪族C5-20多
羧酸)的存在下,通过异构化α-异樟酮形成的。随后,在氧化反应装置2中,-异樟酮在惰性溶剂中与
氧气在氧化催化剂(过渡
金属和N,N′-二
水杨基二胺的复盐)的存在下氧化,从而形成酮异樟酮。在使用蒸馏装置3从反应混合物中去除低沸点组分(杂质,非共轭环状酮)后,通过蒸馏装置4分离出高沸点组分(氧化催化剂),然后在分离装置5中将酮异樟酮与溶剂分离。随后,含有0至5,000 ppm(重量基础)杂质且基本不含酮异樟酮的溶剂通过回收线路6回收到氧化反应中。根据本发明,异构化反应和氧化反应的组合使得可以在保持氧化催化剂活性的同时,从α-异樟酮中生产酮异樟酮。